Infiltration Losses and the Stack Effect

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Homes on average will lose between 20-30% of their conditioned air through infiltration/air movement. Air moves through a home naturally by the “Stack Effect”. The Stack Effect is where heavier higher pressure cooler air in the lower level moves to the upper level/ lower pressure, warmer areas. Since the ground is always higher pressure than the atmosphere, this “Stack Effect” takes place year round. The exiting air must pass through conditioned wall surfaces. Conditioned wall surfaces are exposed to both the outside unconditioned environments and interior conditioned environments. This natural movement of interior conditioned air to the exterior is increased with gaps/poor sealing at the conditioned wall surfaces. Decreasing/eliminating these gaps, especially in attic areas, will reduce the “Stack Effect” on a home and the related energy losses. Additional sealing in basement interior rim joist areas and exterior wall surfaces will further decrease stack effect losses and improve efficiency.

Steps to Follow:

1. Perform an Energy Star inspection to determine your home’s infiltration losses. The inspector must use both an infrared camera and a blower door to accurately determine infiltration losses. 2. Areas commonly found with higher infiltration losses will need to be sealed: • Attic plumbing vent stacks passing through wall top plates. • Flue vents (may require special heat resistant sealing materials). • Ceiling can light gaps where drywall meets can light housing. Can lights should be sealed and rated for insulation contact. • Ventilation exit points (bath and kitchen vents). • All attic wire protrusions through wall top plates (above the electric panel there is typically several). • Interior and exterior wall top plate edges that meet drywall. The exterior wall top plates are critical. • Interior walls with pocket doors historically are more prone to infiltration losses. • Whole house fan surfaces. • Chimney surfaces/areas. Out of service chimneys should be removed and sealed in the attic. • Basement rim joist and foundation wall area(s). • The exterior of conditioned garage walls.

3. Seal areas with foam, extruded polystyrene, drywall mud and caulk. 4. Attic sealing work can be difficult and dangerous, often requiring a third party contractor. Ensure contractor is properly bonded and insured for protection from injury and property damage claims. 5. Schedule an Energy Star follow-up inspection to determine reduced/improved infiltration losses. In my 1998 home, we decreased our infiltration losses by 20-25+%, improving our efficiency and lowering our utility bills.

Eric Skinner (Home Performance with Energy Star) Beaver Builder Supply Holmen, WI (Tom Jenkins-infiltration specialist) May 2011 Carson Dunlop & Associates Ltd (The Illustrated Home) The Home Inspection Company, Inc. DBA Professional Home Inspection Company

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Foam spray extender controls amount dispersed Unsealed top plates of interior walls and helps reach hard to access areas

Sealed top plates of interior walls Sealed top plate & wiring protrusions

Sealing the top plate of an exterior wall Sealing top plates of two intersecting interior walls

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Whole house fan box support for sealing Whole house fan sealed with polystyrene foam

Whole house fan with polystyrene foam, expandable foam and weather stripping for the winter

Recessed can light not sealed Recessed can light sealed with expandable foam

Our Mission Statement: To Help People Make Informed Real Estate Decisions www.phiinspect.com

Out of service chimney losing heat Chimney removed and sealed at floor level

Garage exterior/conditioned walls sealed and painted (drywall seams, and around doors & protrus ions)

Polystyrene board with no expandable foam Polystyrene board and spray foam insulation (rim joist & foundation wall)

Our Mission Statement: To Help People Make Informed Real Estate Decisions www.phiinspect.com

Foam seal (polystyrene and spray foam) in place at all edges, wiring, & plumbing protrusions

Spray foam insulation (open or closed cell) works well to seal crawlspace rim joists and walls

Additional Resources:

For additional details related to extruded polystyrene insulation, open verses closed cell expandable foam, R-Value, other types of insulation and other energy saving resources, facts and ideas please review PHI past newsletter section titled: “Energy Savings Methods & Materials”.

Need More Information? Please visit www.phiinspect.com click our “Post Inspection Support” page and request additional documents.